NUMERICAL SOLUTION OF FLUID-STRUCTURE INTERACTION IN LIQUID-FILLED PIPES BY METHOD OF CHARACTERISTICS

Fluid-structure interaction (FSI) is essentially a dynamic phenomenon and always exists in fluid-filled pipe system. The four-equation model, which has been proved to be effective to describe and predict the phenomenon of FSI due to friction coupling and Poisson coupling being taken into account, is utilized to describe the FSI of fluid-filled pipe system. Terse compatibility equations are educed by the method of characteristics (MOC) to describe the fluid-filled pipe system. To shorten computing time needed to get the solutions under the condition of keeping accuracy requirement, two steps are adopted, firstly the time step Δt and divided number of the straight pipe are optimized, sec-ondly the mesh spacing Δz close to boundary is subdivided in several submeshes automatically ac-cording to the speed gradient of fluid. The mathematical model and arithmetic are validated by com-parisons between simulation solutions of two straight pipe systems and experiment known from lit-erature.     

Synergistic effects of formaldehyde and alcoholic extract of plant leaves for protection of N80 steel in 15%HCl

Abstract

The synergistic effects of formaldehyde and an alcoholic extract of plant leaves have been studied by weight loss measurements at temperatures up to 363 K using various concentration ratios of the two inhibitors to protect N80 steel against corrosion in 15% hydrochloric acid. The inhibition efficiency was found to decrease with increasing temperature for all except two of the various concentration ratios that were studied. After identifying these two most promising mixtures, their corrosion prevention effects for N80 steel in hydrochloric acid were studied in more detail by weight loss and potentiostatic polarisation measurements. The corrosion rate of the steel was decreased by the presence of small additions of the inhibitors. The extent of decrease was found to depend on the nature of the corrosion inhibitor and its concentration. The inhibition efficiencies of the two plant based inhibitor mixtures were compared with those of two commercially available oil industry corrosion inhibitors. In all cases the adsorption of the inhibitors on the steel appeared to follow the Frumkin or Langmuir adsorption isotherm. The inhibition efficiencies of the two plant based inhibitors and the two commercial inhibitors were evaluated at a concentration level of 0.8% for temperatures in the range 303 K to 363 K) and exposure times of between 1 h and 24 h. Thermodynamic parameters including the free energy of adsorption, activation energy, enthalpy and entropy were calculated in both the absence and presence of inhibitors. Potentiostatic polarisation tests have revealed that inhibitors are primarily of the anodic type.     

Adhesion of Pseudomonas aeruginosa to contact lenses after exposure to multi-purpose lens care solutions

Elemental surface compositions of contact lenses were measured after exposure to different lens care solutions (LCS) using X-ray photoelectron spectroscopy and were related to adhesion and detachment of Pseudomonas aeruginosa. Etafilcon A and polymacon contact lenses, prior to and after exposure to LCS were fixed on the bottom plate of a parallel plate flow chamber after which P.aeruginosa #3 was allowed to adhere for 2 h. After adhesion, bacterial detachment was stimulated by perfusing the chamber with an LCS or by passing an air-bubble through the chamber. After exposure to an LCS, the adhesion of P.aeruginosa #3 could either be enhanced or decreased, depending on the contact lens and LCS involved. Initial deposition rates of P.aeruginosa #3 could not be related with changes in elemental surface composition of the contact lenses, but decreased with an increasing ratio of oxygen involved in O C bonds relative to oxygen in O C bonds. P.aeruginosa #3 adhered tenaciously to both types of contact lenses and the passage of an air-bubble through the flow chamber detached only up to 9% of the adhering bacteria. Alternatively, the LCS most effective in decreasing bacterial adhesion after exposure (LCS A), was least effective in detaching adhering P.aeruginosa #3 (8-15%), while the other LCS detached up to 42% of adhering bacteria. In conclusion, different LCS have different abilities to detach the adhering P.aeruginosa #3 from contact lens surfaces and all leave adsorbed components on the surface after soaking. Adsorbed components rich in O C bonds increased adhesion of P.aeruginosa #3 under the conditions used in this study and should, therefore, be avoided.     

A Theoretical Study of Thin Film Delamination Using Clamped Punch-Loaded Blister Test: Energy Release Rate and Closed-Form Solution

Using an exact analytical solution of axisymmetric deformation of a circular membrane centrally connected to a rigid plate under the action of concentrated load at its center, we present an exact formula for the energy release rate applicable to ultrathin film–substrate systems without residual stresses or with small residual stresses. Also, a closed-form solution of axisymmetric deformation of circular membrane under the action of concentrated load at its center is presented.     

Dissolution of Al2Cu phase in non-modified and Sr modified 319 type alloys

Abstract

This study investigates the effects of solution heat treatment on dissolution of the Al₂Cu phase in non-modified and 150 ppm Sr modified 319 type alloys. Experimental and industrial 319 alloys containing different Mg levels (0, 0·3 and 0·6 wt-%) were used for this purpose. Electron probe microanalysis (EPMA) in conjunction with energy dispersive X-ray (EDX) analysis was used to monitor the distribution of Cu in the matrix and to measure the undissolved Al₂Cu phase. In as cast 319 alloys, copper segregates at the dendrite boundaries. The addition of Mg and Sr may cause this segregation to deteriorate. After heat treatment, the copper begins to distribute more evenly across the dendrite as well as in the matrix. The amount of Cu dissolved in the matrix increases with increasing solution time and temperatures, reaching a maximum for the 490°C/8 h solution heat treatment. The dissolution process of eutectic and block like Al₂Cu was also investigated.     

Effect of solution annealing on weldability of aged alloy 800/25Cr–35Ni steel dissimilar welds

Abstract

Dissimilar welding of the aged alloy 800 and the as cast 25Cr–35Ni (wt-%) heat resistant steel was investigated. Microstructures, mechanical properties and weldability of the dissimilar welds were characterised using optical microscopy, scanning electron microscopy and transition electron microscopy equipped by energy dispersive X-ray spectroscopy, and Varestraint test. Since such dissimilar welding was susceptible to crack formation in the heat affected zone of the aged part, the effects of a preweld solution annealing, heat input, interpass temperature and type of filler metal on the weldability of two alloys were investigated. It was found that during the solution treatment, the precipitates produced in the service stage were decomposed and that TiC was formed. In addition, tensile strength and hardness were reduced, but ductility and toughness increased. It was concluded that the most important step to improve weldability and to reduce cracking susceptibility was solution annealing. A suitable annealing treatment was then proposed. The best weldability was found under conditions of solution annealing, low heat input, low interpass temperature and using Inconel 82 or 617 for filler metals.     

Corrosion of stainless steels under heat transfer conditions in nitric acid

Abstract

Novel test rigs are described for the study of the corrosion of metal specimens under controlled heat fluxes. In the corrosion of stainless steels in nitric acid, tests at various heat fluxes with steel surface temperature kept constant have shown that the cooler acid present at the surface under higher heat fluxes leads to slightly smaller corrosion rates than under isothermal conditions. Crevice corrosion can develop under the gasket sealing the stainless steel specimen to the test cell. This crevice corrosion can produce enhanced corrosion rates (by factors up to 100), not only on surfaces within the crevice, but also on those external to the crevice. The factors influencing the development of crevice corrosion are discussed.     

Effects of blending and coating methods on the performance of SIS (styrene-isoprene-styrene)-based pressure-sensitive adhesives

SIS (styrene-isoprene-styrene)-based pressure sensitive adhesives (PSAs) were prepared by melt- or solution-blending. In the coating process, two methods were used: solution coating and melt coating. The performances of the PSAs were found to be different, depending on which of these two blending or coating methods was used. In this study, we investigated the relationship between the viscoelastic properties and the performances of the SIS-based PSAs using different blending and coating methods. Three methods were used: (1) melt-blending and melt-coating, (2) melt-blending and solution-coating and (3) solution-blending and solution-coating. PSAs applied using melt-blending/melt-coating (M—M) have higher peel strength and probe tack than PSAs applied using melt-blending/solution-coating (M—S) and solution blending/solution coating (S—S). However, PSAs applied using M—M blends have lower holding power and SAFT (Shear adhesion failure temperature) than PSAs applied using M—S and S—S blends. The viscoelastic properties and GPC curves of M—S blends were similar to M-M blends, while the peel strength and tack of M—S blends were similar to S—S blends. Therefore, it was concluded that the blending process had more effect on the viscoelastic properties and shear creep of PSAs than the coating process.     

28—THE SPECIFIC HEAT OF WOOL CONTAINING AN ADDITIVE AND THE HEAT OF FUSION OF THE ABSORBED WATER

Specific-heat values are presented, in the temperature range from ?70 to 100°C, for a modified wool at various water contents. The modification was analogous to a dyeing process and involved the uptake of 14% of an additive by the wool. As for untreated wool, an endothermic peak resulting from the fusion of absorbed water was found in the range from ?30 to 0°C. The absorbed water exhibits a sub-division into freezable and non-freezable fractions. Heats of fusion of freezable absorbed water are given and compared with corresponding results for untreated wool. The integral heat of fusion at saturation water content is much less for treated than for untreated wool, as is the amount of freezable water. It appears that the treatment causes the exclusion of a considerable quantity of loosely held water. This is in accord with the concept, derived from Flory–Huggins solution theory, that one effect of the additive is to swell the wool fibres and thereby cause a greater resistance to further swelling at a given water content.     

Experimental study on fine motion control of underwater robots

This paper considers thruster dead zones and saturation limits, which are nonlinear elements that complicate fine motion control of underwater robots. If the vehicle is configured with redundant thrusters, the respective dead zones and their surrounding nonlinear regions could be avoided by implementing a null motion solution for the command input of the vehicle. This solution is derived from the vehicle's geometry and is realized before the application of the motion control algorithm. The result is an improvement in system performance exclusive of the implemented controller type. The approach is illustrated through simulation and experiment with an underwater robot, ODIN.